The field of this invention is downhole choke valves and more particularly, sliding sleeve valves that can be selectively positioned in an open, closed, or other positions in between, from the surface.
It is often desirable to control the flow rate into production tubing from one or more producing zones. Going in the reverse direction, the injection rates from surface tubing into the formation also need to be controlled. One way this is accomplished is with a choke. A choke is a variable orifice. One form of downhole valve or choke is a sliding sleeve valve. In the early days, these valves featured a sliding sleeve with an opening. The sliding sleeve moved between a fully open and fully closed position and could be shifted in a variety of ways. Tools could be lowered from the surface to shift the sleeve or some sort of hydraulic system could be used for that same purpose.
The early sliding sleeve designs lacked the ability to obtain positions intermediate to the fully open and fully closed positions. Accordingly, chokes, not necessarily involving sliding sleeves were developed, which could assume intermediate positions for throttling purposes. One design uses a form of a J-slot mechanism operable by application and removal of hydraulic pressure to selectively align more or less of the ports in a sleeve with the opening in the housing. This design is illustrated in FIGS. 9a and 15 of U.S. Pat. No. 6,308,783. Other designs involve a series of valves operable electrically or hydraulically and mounted in a side pocket mandrel. Examples of this style are the WRFC valve offered by Schlumberger. Schlumberger also offers the TRTFC, which is a choke operating on a form of an indexer pin guiding an indexer to put the valve in different positions. Other well control variable choke devices are illustrated in U.S. Pat. Nos.: 5,823,263; 5,927,401; 5,957,207; 5,979,558; and 6,276,458. Finally, Halliburton manufactures the IV-ICV, which it advertises to be infinitely variable when used in interval control service.
The present invention provides a downhole choke valve that is adjustable in a variety of positions. It features simplicity in design and responsiveness to incremental increases in control system pressure to attain varying degrees of opening. A fully hydraulic and a combination mechanical and hydraulic embodiment are described below. Those skilled in the art will be better able to appreciate the invention from a review of the preferred embodiment described below.
A downhole choke in the form of a sliding sleeve valve operable in a plurality of positions including fully open, fully closed, and positions in between, is disclosed. It features a hydraulic control system that, in one embodiment, provides the motive force to move the sliding sleeve a predetermined amount for a given applied control pressure. Further increments in applied pressure result in further predetermined movements of the sliding sleeve. In another embodiment, the sliding sleeve lands in a series of grooves in the surrounding housing depending on the degree of pressure applied to the control system.